The present invention relates to an arrangement for separating or singling out paper sheets, documents, and similar recording media from a batch, with initially several of the sheets or documents, etc. being moved toward a separating slot with the aid of an intermittent pull-off device and a vibrating device, whereupon the leading recording medium, with the aid of a further pull-off device and an intermittently acting device serving to hold back the trailing recording media, is pulled from the moved batch and fed to the transporting arrangement.
Basically, there exists the danger, in such types of separating devices, that simultaneously two sheets are pulled off, this being due to the fact that the two sheets adhere to one another e.g. on account of electrostatic charges or molecular adhesion. For avoiding such double pull-offs there have already been proposed a great number of solutions. According to one such known principle of solution, the sheets or cards, as pulled from the batch, are pushed through a slot whose opening corresponds to the thickness of the sheets or cards. This arrangement, however, has the disadvantage that only sheets or cards of always the same thickness can be separated which, in addition thereto, must also be unused, because experience has shown that frequently used documents and cards are thicker than new ones because of being folded, creased and soiled during usage. After a more or less long period of circulation, the documents as regards their condition and the paper qualities, will partly differ from one another to such an extent that a mechanical sorting will already appear to be frustrated e.g. by the separating or singling-out problem.
Therefore, it has been suggested by another proposal (German Pat. No. 1,185,628) to guide the document, as pulled from the batch, between two oppositely driven feed rollers so that any eventual second document, also pulled from the batch, will be held back or returned. It is considered one disadvantage of this proposal that the hold-back roller will grind on the extracted document in cases where no second document has also been extracted, so that the forward movement of the document is retarded, thus causing the separating process as a whole to be slowed down.
Another conventional method of making the separation of documents more reliable resides in letting the pull-off or extracted rollers act intermittently upon the batch, which may be effected, for example, with the aid of a cam plate or an eccentric friction wheel (German Pat. No. 1,611,382). In cooperation with a hold-back roller it is already possible in this case to expect a considerable reliability with respect to an individual pull-off, but the German Published Application Pat. (DOS) No. 2,209,483 shows that a separating device of this kind involves a rather considerable investment.
As pull-off rollers, it is possible to use friction wheels or suction drums, with the suction drums having the advantage of more reliably seizing used documents. U.S. Pat. No. 3,300,207 discloses, for example, a vacuum-controlled security document separating device. By this patent it is proposed to use a separating device in which three rectangular sheetmetal members, which are provided with louvers, are displaced with respect to one another, thus closing or releasing the opening of a vacuum chamber. By the to and fro movement of the sheetmetal members the respective document (note) lying closest to the outer sheetmetal member is sucked on and fed to a transporting system. Driving is effected by a motor which, via an eccentric disc, actuates a somewhat expensive lever mechanism. Any second documents also extracted are held back by a vacuum chamber which, with respect to the document batch, is arranged to be staggered in relation to the separating (singling-out) sheetmetal members.
The particular disadvantages of this arrangement are seen in the fact of involving a considerable investment in mechanical means, in which case the compensation of the moving masses is deemed to cause just as many difficulties during manufacture as the prevention of pilot or leakage air between the sheetmetal slides and the vacuum chamber. Of course, the upper limit frequency of ten documents per second is considered to be very good, but finds its restriction in the sequence of movements of the conveying sheetmetal members which have to be accelerated twice and stopped again during each separating process. For the reasons outlines above, this system does not seem to be particularly suitable for being improved. Moreover, the system offers only a small protection against multiple pull-off or extracting operations when considering that, only in the case of double pull-offs, can the second document be held back. In cases where e.g. three documents are moved towards the transporting system, the third document is sucked on while the second one remains unaffected by the hold-back device. Apart from this, the sucking force effecting the holding back must be overcome by the sucking force effecting the separation (singling-out).